Problem: If $x \circledcirc y = x-5y$ and $x \triangleleft y = 4x-3y$, find $6 \circledcirc (2 \triangleleft 1)$.
Solution: First, find $2 \triangleleft 1$ $ 2 \triangleleft 1 = (4)(2)-(3)(1)$ $ \hphantom{2 \triangleleft 1} = 5$ Now, find $6 \circledcirc 5$ $ 6 \circledcirc 5 = 6-(5)(5)$ $ \hphantom{6 \circledcirc 5} = -19$.